1. Field of the Invention
This invention relates to the transport of objects, such as spherical objects, and, more particularly, to a system which communicates objects between a housing inlet and outlet without contact with the housing, and which changes the environment for the object during the transport process, as by changing a fluid within which the objects are entrained.
2. Background Art
It is known to make a semiconductor device by forming a circuit pattern on a silicon wafer and to form semiconductor chips by strategically cutting the wafer. Recent developments have permitted the formation of circuit patterns on a spherical semiconductor, such as a single crystal silicon sphere, having a diameter of 1 mm or less, to thereby form semiconductor elements. For example, to form discrete elements or semiconductor integrated circuits, such as solar cells or light sensors using single crystal silicon spheres, processing steps such as mirror polishing, cleaning, film forming, resist coating, photolithography, and etching, may be performed. To efficiently carry out the overall process, an assembly line may be used in which the processing steps are serially performed. The surface of a single crystal silicon sphere is susceptible to being damaged by contact with a conveying apparatus. Thus, contactless transport is desired.
The processing steps may be performed in different environments, which may contain fluids such as water, different solutions, or active or inert gases. If the processing steps are performed serially at different processing stations, the environment used to transport the object generally must not be delivered to the next processing station. Accordingly, an operation is needed between the processing steps to remove the environment from the previous step and change the environment to one suitable for the next processing step, while transporting the object to be processed to the station for carrying the next processing step out. Reliable, high speed processing is sought in such systems.
If the silicon spheres are transported in irregular intervals from one processing step to the next, or the number of silicon spheres supplied is changed in this type of system, the processing conditions at the various stations must be changed to conform to this transport pattern. Thus, the desired efficiency may be difficult to achieve. Ideally, spherical objects, such as silicon spheres, are processed so that there is a regular interval between steps, thereby allowing the spheres at each station to be supplied in prescribed and regular intervals to the next processing station for performance of the next processing step.
The surface of silicon spheres is easily oxidized, with a film easily formed on the surface thereof. Contact with the conveying system or atmosphere may alter the properties of the top layer. Ideally, transport and processing of the silicon spheres is carried out without contact with the transporting structure and without communication with the surrounding atmosphere.
In one form, the invention is directed to a transport system for a spherical object. The transport system has a supply of a first fluid and a passageway for communication of a spherical object in a path between an inlet and an outlet. At least part of the passageway is bounded by a first tube having a first annular wall with at least one opening through the first annular wall. The first tube guides flow of a spherical object in the first fluid from the inlet towards the outlet. The transport system further includes a source of vacuum in communication with the passageway through the at least one opening through the first annular wall. The source of vacuum produces a low pressure region which causes the first fluid in the passageway to be drawn from the passageway through the at least one opening through the first annular wall. The transport system further includes a supply of a second fluid which is in communication with a spherical object moving between the inlet and the outlet.
The transport system may include a second tube surrounding the first tube so that a chamber is defined between the first tube and the second tube. The second tube has a second annular wall with an opening therethrough. The source of vacuum produces a low pressure region outside of the second tube which causes the first fluid in the passageway to be drawn from the at least one opening into the chamber and from the chamber to and through the opening in the second annular wall to outside of the second tube.
The transport system may include a spherical object to be communicated between the inlet and outlet.
The transport system may include a structure for accelerating the discharge of a spherical object in the passageway from the outlet.
The transport system may include a port through which the second fluid can be introduced at a first location between the inlet and outlet to the passageway in a direction transverse to the path of a spherical object to create a spiral vortex flow of the second fluid around an axis extending generally parallel to at least a part of the path.
The passageway may be defined by a tapered surface having a diameter that increases from the first location towards the outlet.
A second opening may be provided through which the second fluid in the spiral vortex flow and the first fluid picked up by the spiral vortex flow are discharged from the passageway.
In one form, the spiral vortex flow causes the second fluid to flow upstream in the first tube to the at least one opening through the first annular wall so as to be drawn with the first fluid through the at least one opening through the first annular wall.
In one form, the inner tube is made from a porous material that defines the at least one opening through the first annular wall, the inner tube has a surface bounding the passageway and having a first diameter, the spherical object has a second diameter, and the first diameter is slightly larger than the second diameter.
The inner tube may be made from a mesh material.
In one form, each of the first and second fluids is a gas and the spherical object is a single crystal silicon sphere.
A temperature control may be provided for changing the temperature of the second fluid.
In one form, the spherical object and the at least one opening through the first annular wall are relatively sized so that the spherical object cannot pass through the at least one opening through the first annular wall.
The transport system may further include an isolation element which shields a spherical element moving in the path from turbulence generated by the spiral vortex flow.
The invention is further directed to a transport system for a spherical object, which transport system includes a supply of a first fluid and a passageway for communication of a spherical object in a path between an inlet and an outlet. The passageway is defined at least in part by a Laval nozzle having a) a first tapered section with a surface bounding the passageway and having a diameter that decreases in a direction from the inlet towards the outlet, b) a second tapered section with a surface bounding the passageway and having a diameter that increases in a direction from the inlet towards the outlet, and c) a center section between the first and second tapered sections. The transport system further includes a supply of a second fluid and at least one port through which the second fluid can be introduced to the passageway in a direction transverse to the path of a spherical object at a first location between the inlet and outlet so that the second fluid diverges from the first location into both the first and second tapered sections. The outlet is downstream of the second tapered section.
The at least one port is oriented so that the second fluid introduced through the at least one port creates a spiral vortex flow.
The transport system may further include at least one opening communicating from the passageway to externally of the passageway between the inlet and the outlet and a source of vacuum which produces a low pressure region which causes the first fluid and the second fluid in the spiral vortex flow to be drawn from the passageway through the at least one opening.
In one form, the transport system includes at least a second opening communicating from the passageway to externally of the passageway between the inlet and the outlet. The second fluid in the spiral vortex flow communicates through the at least second opening from the passageway to externally of the passageway.
The at least part of the passageway may be bounded by a tube, with the tube being made of a porous material defining the at least one opening.
The transport system may further include a spherical object to be communicated between the inlet and the outlet, with the spherical object and at least one opening being relatively dimensioned so that the spherical object cannot pass through the at least one opening.
In one form, at least part of the passageway is bounded by a tube that is made from a mesh material.
In one form, the spherical object is a single crystal silicon sphere and each of the first and second fluids is a gas.
A temperature control may be provided for changing the temperature of the second fluid.
The transport system may further include an isolation element which shields a spherical object moving in the path from turbulence generated by the spiral vortex flow.
The invention is further directed to a transport system for a spherical object, which transport system includes a supply of a first fluid, and a passageway for communication of a spherical object in a path between an inlet and an outlet. At least part of the passageway is bounded by a first tube having a first annular wall with at least one opening through the first annular wall. The first tube guides flow of a spherical object in the first fluid from the inlet towards the outlet. The transport system further includes a source of vacuum in communication with the passageway through the at least one opening through the first annular wall. The source of vacuum produces a low pressure region which causes the first fluid in the passageway to be drawn from the passageway through the at least one opening through the first annular wall. The transport system further includes a supply of a second fluid which is in communication with a spherical object moving between the inlet and the outlet. The passageway is defined at least in part by a Laval nozzle having a) a first tapered section with a surface bounding the passageway and having a diameter that decreases in a direction from the inlet towards the outlet, b) a second tapered section with a surface bounding the passageway and having a diameter that increases in a direction from the inlet towards the outlet, and c) a center section between the first and second tapered sections. The transport system further has at least one port through which the second fluid can be introduced to the passageway in a direction transverse to the path of a spherical object at a first location between the inlet and the outlet so that the second fluid diverges from the first location into both the first and second tapered section.
The at least one port may include at least first and second ports arranged at diametrically opposite locations relative to the passageway.
The at least one port may be oriented so that the second fluid introduced through the at least one port creates a spiral vortex flow.
The second fluid in the spiral vortex flow may be drawn with the first fluid through the at least one opening. The transport system may further include at least a second opening communicating from the passageway to externally of the passageway between the inlet and the outlet. The second fluid in the spiral vortex flow communicates through the at least second opening from the passageway to externally of the passageway.
The first tube may be made from a porous material that defines the at least one opening.
The first tube may be made from a mesh material defining the at least one opening.
The transport system may further include a spherical object that is a single crystal silicon sphere, and each of the first and second fluids may be a gas.
Temperature control structure may be provided for changing the temperature of the second fluid.
An isolation element may be provided to shield a spherical object moving in the path from turbulence generated by the spiral vortex flow.
The invention is also directed to a transport system for an object, which transport system consists of a supply of a first fluid and a housing defining a passageway for communicating an object in a path between an inlet and an outlet. At least a first opening through the housing communicates from the passageway to externally of the: passageway. A source of vacuum produces a first low pressure region which causes the first fluid in the passageway to be drawn from the passageway through the at least one opening. A supply of a second fluid is in communication with an object moving in the passageway between the inlet and the outlet.
The transport system may include a nozzle, and at least one port through which the second fluid is introduced to the passageway to create a spiral vortex flow in the passageway.
The second fluid in the spiral vortex flow may mix with the first fluid- and move from the passageway through the at least one opening.
The object may be a single crystal silicon sphere, with each of the first and second fluids being a gas.
The invention is also directed to a method of transporting an object within a passageway between an inlet and an outlet. The method includes the steps of directing a first fluid with an object into the passageway through the inlet, creating a low pressure region between the inlet and the outlet, drawing the first fluid out of the passageway into the low pressure region, directing a second fluid into the passageway in a direction toward the inlet so that the second fluid mixes with the first fluid and is drawn out of the passageway into the low pressure region outside of the passageway, and directing the object through the second fluid to the outlet.
The step of directing a second fluid into the passageway may involve directing the second fluid into the passageway so that the second fluid creates a spiral vortex flow.
The object may be directed to the outlet only under the force of gravity.
The object may be a spherical object, such as a single crystal silicon sphere.
The method may further include the step of directing at least a part of the spiral vortex flow from the passageway at a location between the inlet and outlet and spaced from the low pressure region.